Collection and Synthesis of Historical Data from Ocean Weather Station Papa
Total Page：16
File Type：pdf, Size：1020Kb
Collection and Synthesis of Historical Data from Ocean Weather Station Papa Prepared by: Derek Belka Undergraduate University of Washington Civil and Environmental Engineering December 2013 Table of Contents Abstract iii Introduction 1 Data Sources Meghan Cronin, NOAA 2 UCAR Archive 2 Modern Data 3 Resolution and Quality Control of Historical Data Wave Height 3 Wind Speed 9 Position 10 Other Corrections and Comparisons 11 Conclusions and Future Work 12 Appendix A – Summary of Corrections and Adjustments 14 References 15 List of Figures and Tables Figures Figure 1. Full Time Series Wave Data Magnitude Comparison 5 Figure 2. Comparison of Post-1968 Wave Data Magnitudes 5 Figure 3. Comparison of Wave Data Distributions 6 Figure 4. Year-by-Year Comparison of NOAA and UCAR Datasets 8 Figure 5. UCAR Wave Data Statistics 8 Figure 6. Spatial Distribution of UCAR Data Points 11 Tables Table 1. NOAA Ship ID Anemometer Information 10 Table 2. Summary of Parsed Variables and Value Adjustments 14 ii Abstract Meteorological data collection began at Ocean Weather Station Papa (50° N, 145° W) in the 1940s and continued more or less continuously until 1981 when the Canadian government defunded the Ocean Station program. Papa was revived as a permanent observation station in the mid-2000s when researchers at the National Oceanographic and Atmospheric Administration (NOAA) and University of Washington Applied Physics Laboratory (UW-APL) deployed moorings to collect meteorological and oceanographic data at the site. Stakeholders in the modern mission have been searching for a robust, quality-controlled historical dataset to use as a contextual reference for contemporary measurements. This report details the early stages of this process, primarily resolution of available data from several different sources. Ultimately, it was discovered that these seemingly disparate datasets were in fact portions of a more complete dataset archived at the University Corporation for Atmospheric Research (UCAR). Further work will involve more extensive quality controlling, developing historical baselines, and searching for climatic trends. iii Introduction As World War II escalated in the Pacific, the US military began a strategic advantage initiative to develop more accurate weather forecasts for trans-Pacific military and domestic supply lines. This initiative resulted in the establishment of two marine weather-surveying stations, one near Hawaii and the other in the Gulf of Alaska. The latter of these two was originally dubbed ‘Peter’, but was later changed to ‘Papa’ after the NATO Phonetic Alphabet. Ocean Weather Station Papa (OWS Papa, 50° N 145° W) remained under US military control until 1951 when the Navy abandoned the position and the Canadian Coast Guard took over. Ship-based meteorological measurements were taken at OWS Papa almost continuously from the 1940s until 1981 when budgetary restrictions forced the end of the Canadian Weather ship program. During OWS Papa’s active years as a weather ship station, a survey along the commonly used heading to and from the mainland was also established. Later dubbed Line P, the survey was recognized as a valuable research program and Institute of Ocean Sciences (IOS) vessels continued the survey after the Canadian Weather ship program shutdown. The observations catalogued from 1951 to 1981 represent one of the oldest, and longest, contiguous marine weather datasets available today. And yet, the data collected during this time period has not been effectively examined and interpreted, nor has the ocean climate at OWS Papa been quantitatively characterized. This makes the interpretation of modern, shorter datasets more difficult to understand. For example, there may be interdecadal trends at OWS Papa that could lead to misinterpretation of research outcomes from modern observations. Developing and quality-controlling this historical dataset will provide a much-needed contextual reference and scientific tool. This report will detail the early stages of this process that included the resolution of several data sources to a single package, reformatting that package into a more robust instrument of science, and provide an objective assessment of overall data quality. It will also express the author’s opinion of what remains to be done with the dataset and the next steps in the project. 1 Data Sources Meghan Cronin, NOAA In mid-2013, Meghan Cronin supplied several files containing weather ship data collected at OWS Papa (personal communication, May 16, 2013). In a series of emails she expressed that she was uncertain of the data quality as well as its completeness. These files had come to her somewhat circuitously from Howard Freeland, an employee at IOS, who had obtained them from a former staff member’s hard drive. In his own search for the ship-based observations, Howard had also contacted Bill Large of UCAR, who directed Howard to his archived data, though it did not seem to be accessible. Additionally, another IOS employee, who also had a copy of the weather ship data, contacted Meghan in March 2013 but indicated that this was probably the same copy that Howard had retrieved from the retiree. The data came in several different formats, but lacked documentation about quality control. Initially, it was believed that the lack of quality control documentation indicated a relatively raw set of data. A colleague of Meghan’s completed some fairly extensive research and found several articles about the weather ships themselves and distilled them into relevant notes that may prove to be useful interpretation tools. This data is referred to as ‘NOAA data’ for the remainder of this report. UCAR Archive Initially, poor organization and ambiguous file identification prevented the pursuit of this data as a source, but the seemingly improper tampering of the NOAA data, discussed in subsequent sections, led to revisiting the UCAR archive. The data, supplied with documentation but still no quality control information, is stored in large, ASCII-formatted text files containing measurements from roughly half of the ocean stations. Finding, and isolating, OWS Papa from this was relatively easy, albeit time consuming. Distilling the 34 individual variables required parsing each of 93,023 lines of coded observations using the data format described in the National Climatic Data Center’s documentation for DSI-1129 (NCDC, 2003). 2 Modern Data Rather than ship-based observation, modern wave data collection relies on a Datawell directional waverider buoy continuously deployed at OWS Papa and owned by the University of Washington Applied Physics Laboratory (UW-APL). This data is available online through the National Data Buoy Center (NDBC, www.ndbc.noaa.gov) under Buoy 46246. Wind data was supplied by a nearby buoy owned by NOAA and the Pacific Marine Environment Laboratory, also available online through the NDBC webpage under Buoy 48400. Resolution and Quality Control of Historical Data As previously stated, the primary goal of this study is to develop an implementable historical OWS Papa dataset. Cross-examination of the datasets should help determine what overlaps, if any, exist and how these might aid in the determination of the most appropriate data source. Additionally, some datasets may contain different categories of values that may prove useful for interpreting values from other datasets. Initial work has consisted of determining the best raw sources of data and compiling them into a complete, quality controlled data package. It is worth mentioning that the disparate datasets from NOAA were found to be identical data contained in different file formats. Wave Height The NOAA data source indicated a predilection to the belief that the wave height values contained in the provided dataset were suspect and would provide a good starting point for analysis (Cronin, personal communication, May 16, 2013). A preliminary plot of the complete wave height series (Figure 1) showed serious discrepancies when compared to the modern set. The most notable and obvious of these discrepancies is the significant change of magnitude in 1962. A small magnitude of change might be expected in 1968 as wave height measurements prior to that were artificially capped at 9.5-meters because of pre-1968 observation recording techniques. However, this adjustment occurs 6 years prior to its expected date. The dubious doubling of magnitude prior to 1968 also seemed to indicate that these earlier values had been 3 adjusted while the later values had not. The pre-1962 values seemed to be similar in magnitude to modern wave heights, further supporting the conclusion that they had been adjusted at some point. The third plot in Figure 1 shows a correction to the wave height values from 1962 onward, and seems to be more reflective of the modern data, at least in terms of the magnitude. However, there also appears to be a maximum value of 9-meters in the pre-1962 data and not the expected 9.5-meters, indicating there was never a 9.5-meter, or greater, wave height recorded until after 1962 despite 9.5-meter, or greater, wave heights being relatively frequent occurrences in the modern data and adjusted data. The expected 9.5-meter cap notably appears on data from 1962 through 1967, although there was not a single instance of a half-meter value in the pre-1962 data indicating that no half-meter values were ever recorded in this period. While this comparison is revealing in that it exposes several possibly erroneous quality control activities, it does not show a correlation between historical data and modern data characteristics other than local minima and maxima. Figure 2 shows a plot of the NOAA data compared to the modern data on a similar time scale. By isolating a similar time period, it becomes clear that the unadjusted NOAA data is in fact roughly double the modern data. For the remainder of the report, only these corrected values will be considered. A supplemental figure in the appendices shows a similar comparison for pre-1962 and modern data.